Gadenin日本語Get the appSow into cooling soil, not warming soil
Mustard germinates between roughly 45F and 85F (7C to 29C) and emerges in three to six days when the soil sits near 60F (15C). That eagerness is the trap. The seed will sprout in early summer heat just as happily as in autumn, so the mistake is easy to make and only becomes visible weeks later when the plants throw a flower stem at six inches tall.
There are two windows worth using. The first is late winter into early spring, as soon as the soil is workable and above 45F (7C). The second, and by far the better one, is from the point where summer heat breaks through until about eight weeks before your first hard frost. Plants growing into shortening days and cooling nights do not bolt, and the leaves stay broad and tender instead of turning into narrow, fiery straps.
Sow a quarter of an inch (5 mm) deep, a half inch (12 mm) at the very most. The seed is tiny and the seedling has almost no reserve to break a crust. If your soil caps after rain, cover the drill with sieved compost or old potting mix rather than the clods you dug out, and water with a fine rose so you do not wash the seed into the crevices.
| Soil temperature | Days to emerge | What to expect |
|---|---|---|
| 45F (7C) | 9 to 14 | Slow, but stands are even and seedlings are stocky |
| 55F (13C) | 5 to 7 | Reliable; the usual autumn and early spring case |
| 60F (15C) | 3 to 5 | The best balance of speed and quality |
| 75F (24C) | 3 | Fast and leggy; expect early bolting |
| Above 85F (29C) | Erratic | Patchy germination and near-certain bolting; wait |
Decide the picking style before the seed goes in
Mustard is grown two entirely different ways from the same packet, and the spacing is the only thing that decides which you get. Sown thick and cut small, it is a baby leaf crop: mild enough to eat raw, ready in three to four weeks, and cut with scissors an inch above the crown. Sown wide and left to size up, each plant makes a broad rosette twelve to eighteen inches (30 to 45 cm) across, and the leaves are far too hot to eat by the handful but excellent cooked.
The heat concentrates as the leaf ages, so this is not just a size difference. A baby leaf bed and a full-size bed are, in flavor terms, two separate vegetables. Grow both if you can, but grow them as separate sowings rather than trying to take one out of the other.
For baby leaf, drill or scatter so plants stand about one inch (2.5 cm) apart in rows four to six inches (10 to 15 cm) apart, and do not thin at all. For full-size plants, thin ruthlessly to eight to twelve inches (20 to 30 cm) each way. Crowded full-size mustard yellows from the inside and collapses at the first prolonged wet spell.
| Growing style | Final spacing | First cut | Best use |
|---|---|---|---|
| Baby leaf | 1 in (2.5 cm) | 21 to 28 days | Raw in salad; shear the band whole |
| Medium | 4 to 6 in (10 to 15 cm) | 30 to 40 days | Wilted into eggs, pasta, noodles |
| Full size | 8 to 12 in (20 to 30 cm) | 45 to 60 days | Braising and long cooking only |
Thinning is the step people skip
Because mustard germinates so well, a row sown at a sensible rate still comes up looking like a lawn. Thin twice. The first thin comes when the seedlings have their first true leaf, taking them to about two inches (5 cm) apart. The second comes two weeks later at the final spacing, and the thinnings from that round are a perfectly good salad in themselves.
Thin by pinching or snipping at soil level rather than pulling. Mustard roots tangle at that density and pulling one seedling lifts three neighbors, leaving them to check for a week. Do the work in the evening or after rain when the bed is damp, and water the row afterwards to settle the soil back around the roots you kept.
- Water the drill before sowing, not after Run water into the open drill, let it soak, then sow into the damp bottom and cover with dry soil. In warm weather this keeps the seed zone cool and even, and it stops the surface capping over the seedlings.
- Sow short rows every two weeks A single big sowing gives you a glut and then nothing. Two feet (60 cm) of row every fortnight through the good season keeps a steady supply and means one bad sowing never costs you the whole crop.
- Mark the row and note the date Write down the sowing date and the position of each short row. When you compare those dates against when each row bolted, you get your own cutoff for spring sowing instead of a guess from a packet.
Volunteer seedlings from last year's plants come up thickly and for free, but they come up when the parent plant decided, not when you did. Treat them as a bonus baby leaf crop, and do not count on them for a full-size stand.